In the United States, rates of postpartum retention in care and viral suppression are extremely poor among women living with HIV (WLH). In Philadelphia, PA, from 2005 to 2011, only 39% of WLH were retained in HIV care during the first year following delivery and that number had dropped to 25% at year two. Retention rates in the South are similar, ranging from 37% in Mississippi (1999-2006) to 47% in Atlanta, GA (2011-2015). Retention in HIV care particularly affects black and Hispanic women as they are disproportionately affected by the HIV epidemic. Retaining WLH in care positively impacts their well-being and health postpartum and for years to come, which promotes not only their health but that of their newborns. Through a critical review of research literature, we found that interventions to improve maternal retention have been implemented in low- or moderate-resource countries, but studies in high-resource countries are lacking. In sub Saharan Africa, the use of peers has resulted in significantly higher maternal retention and viral suppression compared to standard of care. Peers are WLH who remained engaged in HIV care postpartum, and provide education and support to WLH in the prenatal and postpartum periods. We propose to test the efficacy of a theory-driven peer intervention, based on the integrated model of health behavior, through a multi-site randomized control trial (RCT). The peer intervention?Women Involved in Supporting Health (WISH)?is designed to increase self-efficacy, social support, self-regulatory behaviors, and outcome expectancy in order to improve retention in care and viral suppression postpartum. The intervention is an adaptation of the International Center for AIDS Care and Treatment peer curriculum, developed for sub Saharan African pregnant WLH. It will consist of 3 face-to-face prenatal sessions to address barriers to outcome expectancies and self-efficacy in the third trimester and 6 face-to-face postpartum sessions scheduled up to 3 months postpartum. The postpartum sessions build on outcome expectancy and knowledge acquired in the prenatal sessions to develop skills tailored toward increasing ART adherence and engagement in HIV care after delivery. The multisite RCT will take place across Center for AIDS Research sites in Philadelphia, Washington DC, Atlanta and Birmingham, all cities where HIV infection rates remain disproportionally high among black and Hispanic women. A total of 260 pregnant WLH will be randomized to either the WISH intervention or to an attention- matched health-awareness control group. Primary and secondary outcomes include retention in HIV care and viral suppression at 1 year postpartum. The study will also evaluate how theoretical variables (self-efficacy, social support, self-regulation, outcome expectancy, and depressive symptoms) mediate study outcomes. The impact of this research will be the development of the first evidence-based peer intervention to address the pressing need to improve postpartum retention in HIV care and viral suppression of WLH in the United States.